Creating a Soft Body Surface that Responds to Different Masses of a Rigid Body Object
To do this: You would need one plane to serve as the cloth, and one UV Sphere to serve as rigid body. You would have to give the plain a cloth simulation (as soft body isn't what you want), and then the the UV Sphere a rigid body and collision. I am assuming that you know the cloth and rigid body settings, as I am not going to go over that. 

Then, you would subdivide the plane as many times as the quality that you need/want. 

For the next step, you would need to place the UV Sphere directly over the plane. Then, you can change the mass of the UV Sphere in the Rigid Body Simulation, and then when you play your animation using Alt-A or the Play Animation button, then the plane will deform accordingly. 

Then, select the plane and the UV Sphere with Shift-Right-Click, press Alt-D, and then place them wherever you want the second DIFFERENT set to be. Next, in the Rigid Body Simulation tab, just change the mass accordingly. 

Hope this helps!!!

Note: If this doesn't work, then remove the Rigid Body Simulation, keep the Colision though, and insert keyframes on the start and end of where you want the UV Sphere(s) to start/end.